Two of the most commonly used ingredients in topical treatments are Benzoyl Peroxide (BPO) and all trans Retinoic acid (Tretinoin (ATRA)) which can be very effective in treating mild to moderate cases of non-inflammatory acne. Benzoyl peroxide acts by destroying P. acnes, the bacteria that causes the condition acne. It acts as an antiseptic and as an oxidizing agent, reducing the number of comedones, or blocked pores. Tretinoin (ATRA) is a unique topical medication used in the treatment of acne that allows the keratin plugs of microcomedones to be expelled, thus fewer lesions are able to rupture and cause papules, pustules and nodules of inflammatory acne. A combination drug of BPO and ATRA should have both comedogenesis and bacteriostatic effect in acne treatment. However, two main obstacles to such combination is instability of ATRA in presence of BPO and severe adverse events such as erythema, irritation, burning, stinging, scaling and itching.
Compositions and methods for treatment acne comprising BPO and/or a Retinoid are described for example in U.S. Pat. Nos. 4,350,681, 4,361,584, 4,387,107, 4,497,794, 4,671,956, 4,960,772, 5,086,075, 5,145,675, 5,466,446, 5,632,996, 5,767,098, 5,851,538, 5,955,109, 5,879,716, 5,955,109 5,998,392, 6,013,637, 6,117,843, Pub. No.: US 2003/0170196, US2002064541, and 20050037087. H. Tatapudy et al., Indian Drugs, 32(6), 239-248, 1995, describes benzoyl peroxide microcapsules, prepared by coacervation phase separation process.
Sol-Gel process has been used to encapsulate various active ingredients, thus isolating the active ingredient from the environments.
U.S. Pat. Nos. 6,303,149, 6,238,650, 6,468,509, 6,436,375, US2005037087, US2002064541, and International publication Nos. WO 00/09652, WO00/72806, WO 01/80823, WO 03/03497, WO 03/039510, WO00/71084, WO05/009604, and WO04/81222, disclose sol-gel microcapsules and methods for their preparation. EP 0 934 773 and U.S. Pat. No. 6,337,089 teach microcapsules containing core material and a capsule wall made of organopolysiloxane, and their production. EP 0 941 761 and U.S. Pat. No. 6,251,313 also teach the preparation of microcapsules having shell walls of organopolysiloxane. U.S. Pat. No. 4,931,362 describes a method of forming microcapsules or micromatrix bodies having an interior water-immiscible liquid phase containing an active, water-immiscible ingredient. Microcapsules prepared by a sol-gel process are also disclosed in GB2416524, U.S. Pat. No. 6,855,335, WO03/066209.
There still is a widely recognized need for a composition comprising BPO and retinoid in which the active ingredients are chemically stable when formulated together in the same composition.